Arsenic is widely dispersed in the earth's crust and is released into the air, soil and water by human activities such as mining, smelting, manufacturing and pesticide application. Epidemiological studies suggest that exposure to arsenic in drinking water increases the risk of mortality from cardiovascular disease (CVD). Ingestion of arsenic produces reactive oxygen species (ROS) and reactive nitrogen species (RNS) in tissues. ROS/RNS may exacerbate CVD by altering vessel wall physiology through regulatory pathways that include eicosanoids, growth factors and nitric oxide. We propose an investigation of the potential for arsenic to increase morbidity and mortality from CVD with a focus on atherosclerosis, or coronary artery disease (CAD). The overall objective of this application is to identify the mechanisms and regulatory pathways involved in arsenic-induced CAD. The central hypothesis is that arsenic facilitates development of CAD. The specific aims for testing this hypothesis are 1. characterize arsenic-mediated formation of reactive species in endothelial cells, 2. define changes in expression of key atherogenic regulatory molecules in endothelial cells upon treatment with arsenic, and 3. determine the effects of arsenic on expression of key CAD regulatory molecules in the ApoE(-/-) atherosclerotic mouse model. An important ROS/RNS is peroxynitrite, a powerful oxidant that is capable of nitrating tyrosine residues. Peroxynitrite and nitrotyrosine formation will be the primary focus of the endothelial cell studies in Specific Aim 1. In Specific Aim 2 (endothelial cells) and Specific Aim 3 (mouse), expression of inflammatory regulators including cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX) and inducible nitric oxide synthase (iNOS) will be assayed. The eicosaniod products of COX-2 and 5-LOX will also be measured along with pertinent growth factors and cytokines. Antioxidants and enzyme inhibitors will be used throughout these studies to elucidate the most important pathways in arsenic-induced atherogenesis. These studies will provide important data for determination of health risks associated with arsenic exposure and potential CAD prevention strategies.